| 摘要 |
PURPOSE:To make equal the influence of the sample surface reflecting ratio, to cancel the effect and to execute the high accuracy by preventing the interference of two detecting systems and detecting the projection pattern at the same place on the sample. CONSTITUTION:A projection pattern mask 3 is one piece, and one pattern projected on a sample 6 surface by image sensors 9 and 11 dislocated and arranged in the optical axis direction is detected commonly. As the result, the interference of two detecting systems is prevented, the sample surface reflecting ratio is also the same to detect the projection pattern of the same place on the sample 6, and as the result, the effect is cancelled. Thus, the point where the contrast of both detecting systems, the focusing target position, is equal, is not changed, nd the focusing position detection can be executed with a high accuracy. |
