| 摘要 |
PURPOSE:To make an easy and high-precision alignment possible in any magnification, by providing a focusing screen and a lens of variable magnification between an object lens and a prism and image-forming reference marks and alignment marks onto the prism. CONSTITUTION:The first focusing screen 23 having a reference mark 23a and a relay lens 25 of variable magnification are provided between the first object lens 21 and a right-angled prism 30. The first alignment mark 3 of a wafer 1 is projected onto the focusing screen 23 and is projected onto a slope 31 of the prism 30 together with the reference mark 23a by the lens 25. The second alignment mark 4 is projected onto a slope 32 of the prism through the same course also, and these four images are observed by an eyepiece 36. In this constitution, even if the magnification is raised, reference marks 23a' and 24a' are magnified without changing center positions. Thus, an easy and accurate alignment due to magnified images is possible independently of magnifications. |
