| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect wide-area defects. SOLUTION: A single-issued defective signal is added to an integrated value of an integrated value memory 33 by an adder 31, and the added value is stored in the integrated value memory 33 as an integrated value. The continuity of the single-issued defective signal is determined by a continuity determining device 36. In the case of the absence of specific continuity, a select signal is outputted to a selector 32 to set the integrated value of a corresponding lane of the integrated value memory 33 at zero via a data zero generator 35. The integrated value from the adder 31 is compared with a threshold value by a comparator 37. When the integrated value becomes equal to the threshold value, a wide-area defect signal is outputted. A continuity set value is changed at a continuity setter 39 and set at an appropriate value according to the frequency, size, etc., of the defects. The wide-area defects are accurately detected according to the frequency, etc., of single defects.
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