| 摘要 |
PURPOSE:To correct variations in magnification and image formation surface with high precision by providing an air chamber which is shielded from the outside air at at least one position between lens element of a projection objective lens, and further providing a pressure controller which controls the pressure of the air chamber. CONSTITUTION:Four air rooms (J, K, L, and M) corresponding to the 11th space (k), the 12th space (l), and the 13th space (m) are coupled by a communication part 11a in the projection objective lens 1, and shield from the atmosphere, an its pressure is controlled through a pipe 11 as a pressure control space. Then, a pressure controller 12 is supplied to air having constant sationary pressure from a pressurized air supplying device 4 through a filter 13 and the air is discharged by an exhaust system 8 when necessary. Consequently, variations in magnification and image forming surface are corrected with high precision. |
