| 摘要 |
PURPOSE:To keep the state of image formation at a specified state even if the distributing state of lighting luminous flux is changed, based on the data from an input means, in which the change in a distributing state of the lighting lumnous flux is inputted, by correcting parameters for obtaining the change in optical characteristics of an optical projection system, and correcting the state of the image formation. CONSTITUTION:In correspondence with the preset numerical aperture of a lighting aperture stop 18, an applicable time constant is selected out of a memory 42 by a selector 40. The selected time constant is inputted to a main controller 28. The amount of fluctuation of a magnification is obtained based on the time constant. Based on the amount of fluctuation and a pressure in a tightly sealed lens chamber 24F, which is selected by a pressure sensor 38, a control signal is outputted from the main controller 28 to a pressure regulator 32. A pressure applying system 34 and an exhausting system 36 are utilized, and the pressure in the tightly sealed lens chamber 24F is controlled. Thus a projecting lens 24 is controlled so that the magnification of the lens 24 becomes the specified value.
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