| 摘要 |
PURPOSE:To enable to change over image formation magnification and to relatively inexpensively constitute the subject optical system without using a number of expensive objective lenses by changing over image formation lenses without changing over an objective lens. CONSTITUTION:When an image formation lens 41 is now selected and set up on an optical axis, a slit image is formed on a sample 6 at the reduction ratio M=f2/f1. An image formation lens 42 is then selected, machining is performed at its ratio with the same slit width according to its focal distance. Namely, the image formation magnification can be freely changed over by changing over freely the desired number of image formation lenses 4 with the different focal distance with an objective lens 5 fixed. Accordingly, the desired machining size can be obtained. When it is required to use the expensive objective lens 5 as in the case of using an ultraviolet laser beam, the image formation optical system can be constituted relatively inexpensively without using a number of expensive objective lenses. |
