An optical arrangement includes a diffractive optical element and a curvature control system for changing curvature of the diffractive optical element. The optical arrangement can be incorporated into an exposure apparatus having an illuminating system for illuminating a mask having a pattern formed thereon and a projecting system for projecting the pattern of the mask onto a wafer, such that the projecting system includes a diffractive optical element and a curvature control system for changing curvature of the diffractive optical element.