| 摘要 |
PURPOSE:To prevent the erroneous recognition of foreign objects by providing the first register group having the same bit legnth as the divided number of addresses in the rotating direction of the face plate specimen and separately providing a shift register group which corresponds to each register in the first register group. CONSTITUTION:The shift register group 20 sequentially delays the signal at every rotation. The bit length of the shift registers 20a, 20b, and 20c are selected so that the bit length is equal to the divided number of the addresses in the rotating direction of the face plate specimen 3. The register group 21 extracts the local area of the face plate specimen 3, and the bit length thereof is determined by the connected length of the foreign objects. In this constitution, even though one foreign object is detected in a plurality of addresses in the bi-dimensional memories, said foreign object can be accurately recognized as one foreign object, and the accurate counting of the objects can be performed. |
