| 摘要 |
PROBLEM TO BE SOLVED: To minimize variation of illuminance when illumination conditions are altered and to correct variation of illuminance inherent to each projection aligner. SOLUTION: Effect z of an optical filter 17 can be represented by z=a(x2+y2). When the optical filter 17 is moved two-dimensionally along a plane perpendicular to the optical axis, a variation of one-dimensionally inclining illuminance distribution can be generated. Illuminance at the meshed part on fig. 7 (C) is thereby measured previously and used as basic data. The ND filter 17 is moved by a specified distance d0 in the X direction and Y direction and variation of illuminance is measured, variation of illuminance is calculated at four points on the periphery of a plane to be irradiated and the effect of variation is stored when the ND filter 17 is moved. Moving direction and amount of the ND filter 17 are then calculated based on the effect. Finally, the filter 17 is driven by a specified amount in a specified direction through an optical filter drive mechanism 18 based on the calculation results.
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