Patent ID: 7746575

Claim:
A method of reducing an aberration in an optical system for projecting a pattern on a reticle or a mask onto an object, the optical system having a lens for removing the aberration, the lens being able to adjust a tilt angle relative to an optical axis, the method comprising the steps of: measuring the aberration in the optical system; and calculating a tilt angle of the lens relative to the optical axis to reduce the aberration when the aberration is outside a permissible range; inclining the lens relative to the optical axis based on the tilt angle calculated in the calculating step with an optical support mechanism coupled to the lens, the optical support mechanism having a forcing member, a first support member supporting the lens, and a second support member coupled to the first support member via the elastic member, by applying a force to the elastic member via the forcing member to adjust at least one of a position or an orientation of the lens, where the forcing member applies an offset force to elastically deform the elastic member substantially in a radial direction of the lens so that an offset force from the forcing member twists about a rotational axis perpendicular to both the radial direction of the optical element and an optical-axis direction of the lens.