| 摘要 |
PURPOSE:To improve accuracy on the detection of the position of the mark, and to shorten detecting time by limiting an arithmetic region of a matched filter, etc. and shortening arithmetic time. CONSTITUTION:The primary moment mO' of sections larger than a fixed level A of mark signals 4 acquired when the mark 1 is scanned by electron beams 2 is obtained by a primary moment counter circuit 7. The arithmetic region of the matched filter is limited within a narrow range before and behind the central position mO of a rough mark by an arithmetic circuit 9 to shorten arithmetic time, signals of a high SN ratio are acquired, and the primary moment mO of sections larger than a fixed level B is obtained by a primary moment counter circuit 10. Both primary moment are computed in a short time, and the primary moment mO represents the accurate central position of the mark signals 4. |
