| 摘要 |
PURPOSE:To make focussing of a projection optical system highly accurate over the whole range of an object to be exposed, by conducting the focussing of the projection optical system on the object to be exposed in accordance with the variation of a sum of intensity of plural beams of light detected by a photo-electric conversion means. CONSTITUTION:When an object 2 to be exposed is arranged at the optimum position of a projection optical system 6, the position relation between light sources 8 and 9 and the object 2 to be exposed and the like is set as follows; positions of the loops or the nodes of the respective standing waves of plural beams of light 8a and 9a, whose wavelengths are mutually different, between the object 2 to be exposed and photo-electric conversion means 13 and 14 are made to coincide with the positions of the photo-electric conversion means 13 and 14. That is, the sum of intensity of the plural beams of light 8a and 9a detected by the photo-electric conversion means 13 and 14 is made maximum or minimum. In this manner, the focussing of the projection optical system 6 in the whole range of the object 2 to be exposed can be performed with high accuracy in accordan with the sum of intensity of plural beams of light 8a and 9b detected by the photo-electric conversion means 13 and 14. This can be done without influences of the warp and unevenness of the object 2 to be exposed and, further, its position in the system. |
