| 摘要 |
PROBLEM TO BE SOLVED: To quicken focusing operation on a sample on whose surface a light transmissive film is formed. SOLUTION: The respective contrast values c<SB>10</SB>, c<SB>11</SB>and c<SB>12</SB>of respective image data successively picked up when a sample stage 1 is made to descend stepwise are compared with a preset threshold Th. When the contrast values c<SB>10</SB>, c<SB>11</SB>and c<SB>12</SB>are less than the threshold Th, the sample stage 1 is made to descend stepwise by 1st pitch interval width Ha, and when a contrast value c<SB>13</SB>is more than the threshold Th, the sample stage 1 is made to descend stepwise by switching pitch interval width to 2nd pitch interval width Hb smaller than the 1st pitch interval width Ha, and when the contrast value exceeds a peak, the sample stage 1 is made to ascend stepwise by the 2nd pitch interval width Hb and restored to a height position attained when a contrast value c<SB>15</SB>of the peak is obtained. COPYRIGHT: (C)2006,JPO&NCIPI |
