| 摘要 |
PURPOSE:To project the image on a reticle on a base plate at an accurate magnification, by maintaining the spaces among reducing projection lenses in vacuum states so as to prevent the refractive indexes of the gaseous phases among the lenses from being changed. CONSTITUTION:Reducing projection lenses 3, 3... are set in a lens barrel 7 and vacuum packings 8 are fitted to the periphery of each lens so as to maintain the space between each lens in a vacuum state. When a ray of light (line g or i) for projection is made incident to the lenses 3, no temperature rise and pressure fluctuation take place and, accordingly variation of refractive indexes can be prevented in the spaces 4 among the lenses 3. Therefore, the rays of light is not bent as shown by the dotted line, but always projected on a semiconductor base plate 5 through the optical path shown by the solid line. Therefore, an image on a reticle 2 can be projected on the base plate 5 at an accurate magnification. |
