DIMENSION ERROR DETECTION IN OBJECT

In a system for real-time inspection of patterns formed on a base, the pattern including surfaces and edges. The system provides for a detector that includes: (i) two input channels for receiving streams of pixels representing the patterns. Each pixel representing the surface and/or edge of the pattern in sub-pixel boundary, (ii) two line width measurement devices being responsive to the streams of pixels for processing in real time the pixels in a manner that corresponds to a predetermined direction in the patterns, so as to measure, in sub-pixel boundary, line width data between two edges. This measurement is effected by executing the following steps: (i) detecting an opening edge, (ii) successively updating line width; and (iii) providing a line width measurement in response to detecting a closing edge. The detector further includes comparator being responsive to the line width data delivered from the two line width measurement devices, for comparing the line width data and obtaining difference between them, so as to generate a defect.backslash.no defect indication depending upon the difference.