| 摘要 |
PURPOSE:To correct magnification errors and fluctuation of a focal point due to the fluctuation of temperature and atmospheric pressure simply, by providing a gaseous lens, in which a gas having a refractive index different from outer air, in a light path from a mask to a substrate, on which light is projected. CONSTITUTION:An annular frame 4, in which two transparent thin films 3a and 3b are provided with a specified interval being provided in the direction of a light axis, is provided in a light path between a mask M and a projecting lens 5. In a space between the thin films 3a and 3b, a gas, which has a refractive index different from that of outer air and has specified pressure, is sent from a gas supplying and exhausting means 11 through a pipe 10. A controller 16 detects the difference between the inner pressure and atmospheric pressure and outputs a control signals S3 to the gas supplying and exhausting means 11 so that said pressure difference becomes a specified value. When the pressure difference is changed, the curving amounts of the thin films 3a and 3b are changed, and the power of the gaseous lens formed by an airtight space 3 is changed. Therefore, the substantial length of the light path between the mask M and the projection lens 5 is changed. |
