| 摘要 |
The surface of a printed circuit is optically scanned and the data acquired, after some preprocessing, compared to reference data representing a fault-free printed circuit. The preprocessing involves a reduction of the conductivity of the lines in the circuit to connectivity of particular features of the lines. The comparison is carried out by establishing a correspondence between global labels in check points of a certain type, and pre-computed reference global labels in corresponding points, and the global labels of other check points are compared with corresponding ones of the reference, with any miscorrespondence indicating a defect of the 'open circuit' type, while any merge event between different global labels indicates a defect of the 'short circuit' type. The apparatus consists of an optical front end (1) having a data acquisition scanner and pre-processor (6); a signal distributer (2) comprising a first look-up table (8), a transformation unit (9) and a second look-up table (10); a reference comparison subsystem (4) comprising a reference disk (11), a decompressor (12), a comparator (13) and a micropocessor (15); and a general conductivity analysis subsystem (3) comprising a second level signal processor (17) and a host computer (14), the said subsystems being connected to a main host computer (5). |
