| 摘要 |
PROBLEM TO BE SOLVED: To cancel the focusing characteristic change due to a wavelength variation by detecting the part of a pulse illumination light, calculating the change of optical characteristics, and correcting the change of a focusing state corresponding to the change of the focusing characteristics. SOLUTION: The atmospheric pressure and temperature of the vicinity of an etalon 22 are measured by a measuring unit 10, and the result is sent to a controller 9. The controller 9 calculates the wavelength change amount of a laser beam passed through a projection lens 6 on the basis of the measurement signal from the unit 10, and calculates the correcting amounts of the magnification and focusing position. When the correcting amount of the magnification change is calculated, the controller 9 outputs the correcting value to a pressure regulator 11. The regulator 11 so control the pressure of an air chamber 12 as to generate the differential pressure to cancel the magnification change. Thus, the influence of the wavelength change is not so effected as to affect the focusing characteristics. |
