OPTICAL UNIT, OPTICAL SYSTEM EQUIPPED WITH OPTICAL UNIT, MANUFACTURE OF OPTICAL UNIT, EXPOSURE DEVICE INCLUDING OPTICAL SYSTEM EQUIPPED WITH OPTICAL UNIT, AND MANUFACTURE OF DEVICE USING EXPOSURE DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an optical unit (and a stepper equipped with the unit) which does not have its attitude limited when used and has a very large degree of freedom at the time of installation. SOLUTION: This optical unit is equipped with a diffracting optical element 3 which has an optimum function when deforming by receiving internal pressure, which is prescribed in a sealed space 34. Namely, dry air, helium gas, nitrogen gas, etc., are charged to positive pressure so that when external force variation including relative gravitational variation is applied to the optical axis of the diffracting optical element 31, the elastic deformation quantity of the diffracting optical element 31 becomes nonlinear and the diffracting optical element 31 is held nondestructive.