| 摘要 |
PURPOSE:To shorten a downtime by a method wherein exposure processing is interrupted when a predicted information specifying the fluctuation of imaging characteristics is dissipated, the fluctuation of imaging characteristics is observed at a plurality of points on a time base, a precise predicted information is computed and correction control is restored when a mask pattern is projected and exposed and processed. CONSTITUTION:A signal S1 displaying the ratio within the unit time under the open state and close state of a shutter 2 is inputted to a pressure regulator 20 for correcting the fluctuation of optical characteristics by the incidence of the lighting beams of a projection lens 5 from a control circuit 21 for the shutter 2. Data, such as a time constant on the magnification fluctuation characteristics of the projection lens 5, the amount of light of transmitted lighting beams, magnification variation to the quantity of pressure regulation, etc. are memorized previously to the pressure regulator 20. The pressure regulator 20 computes the magnification variation of the projection lens 5 at that time on the basis of these data and predicted informations capable of momently changing, calculates a pressure value correcting the variation and controls the pressure of an air chamber 5a. Accordingly, when informations corresponding to incident hysteresises dissipate, correction control can be restored rapidly to the correction control of imaging characteristics having high precision.
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