Abstract: A technique and exposure apparatus measures, with a high degree of accuracy, figure and placement errors of individual optical elements constituting optics embedded inside of an exposure apparatus or the like, with the optics kept in an embedded state as they are. The system measures the distribution of wavefront distortions in the optics while changing the positions of a light source and an image point inside an exposure field of the optics being observed. Optimal displacements of reflective surfaces constituting the optics are then found by calculation based on the measured distribution of wave-front distortions. Finally, the positions of the reflective surfaces are corrected in accordance with the calculated optimal displacements. The positions of the reflective surfaces are corrected by individually controlling displacements output by a plurality of actuators attached to each reflective surface and by mechanically modifying appropriate portions of the reflective surfaces.

Abstract: A separation type optical head according to the present invention includes at least a light source portion for emitting collimated beams, a focusing device (a focusing lens) for focusing the collimated beams onto an information recording surface of an optical disc medium, a focal point control mechanism for the position of the spot on the information recording surface, and a photo-detection portion for receiving beams reflected by the information recording surface. The structure is divided into a fixed portion including the light source portion and the photo-detection portion and a movable portion including the focusing device (focusing lens) and the focal point control mechanism. At least the movable portion of the separation type optical head is movably accommodated n a frame (sealing case) for the optical head so as to prevent irregular vibrations of the movable portion due to high speed air flows or turbulence.