| 摘要 |
PURPOSE:To automatically detect an entry of a noninspection object within a mask region and automatically reset an optimal mask region by providing the first and second latch circuits to latch the horizontal coordinate of a vertical mask line and comparing horizontal coordinates for the first and second latch circuits. CONSTITUTION:An X coordinate for horizontal scan is always supplied to a latch circuit 2 from an X coordinate generating coordinate. Consequently, the latch circuit 2, when receiving a latch pulse LTCH1 from ''AND'' gate 13, latches an X coordinate for an X coordinate generating circuit 1. That is, with regard to an object which cuts a mask line an X coordinate of a transition point from an object to a background, e.g. a coordinate (X1, n) is latched on the latch circuit 2. In the meantime, a coordinate (X1, n-1) is latched on a latch circuit 4. A comparison circuit 3 compares the respective latched contents of the latch circuits 2, 4 and, if the latched content represents X1, n>X1, n-1, outputs a logic 1 to an AND gate 5. |
