The present invention relates to a three-dimensional shape detecting apparatus utilizing a light segmenting method for testing if there is a defect in soldered areas of a printed circuit board, such as imperfect soldering, oversoldering or pinhole, if a bump in LSI bonding process is proper or not, or if circuit components or IC chips are mounted on a substrate with a proper orientation and at a proper position.
Heretofore, when the shape of a miniature three-dimensional object of an industrial product having a miniature three-dimensional shape on a plane such as a soldered area on a printed circuit board, a component mounted on the printed circuit board or a bump in a LSI bonding process is to be examined, an operator views by his eyes directly or through a magnifying lense or a stereoscopic microscope. However, since the soldered area on the printed circuit board has a three-dimensional shape and unstable surface condition such as glaze on the surface or partial blue, it is difficult to examine in a stable manner and failure of detection and difference of determination criterion among the operators have been unavoidable. As to the component mounted on the printed circuit board, it also has a three-dimensional shape and in addition has a surface of mixture of various reflection coefficients, and hence the stable examination has not been attained.
The Japanese Published Unexamined Patent Application No. 48-7764 disclose a light segmenting method in which a brightest point in a video signal produced by a television camera is detected. However, this method cannot exactly detect a three-dimensional shape. The Japanese Published Unexamined Patent Application No. 49-39445 disclose a light segmenting method in which a video signal produced by a television camera is digitized. This method also cannot exactly detect the three-dimensional shape.