LENS ABERRATION MEASURING INSTRUMENT AND LENS TILT ADJUSTING DEVICE USING SAME

摘要

PROBLEM TO BE SOLVED: To measure the comatic aberration of an optical system in real time so as to adjust the tilt between a disk and an objective so that the comatic aberration of the objective is corrected. SOLUTION: The light from the objective 2 is converged on a reflective diffraction element 3 to observe the intensity distribution of the reflected light and a push-pull signal when the reflective diffraction element 3 is swung at right angles to a diffraction grating is detected. A photodetector 4 which detects the reflected light divides a right and a left interference area into inside and outside areas and 1st to 4th quadratures, i.e., 16 areas in total and detects the radial comatic aberration from the phase difference between the push-pull signals of the inside and outside areas and the tangential comatic aberration from the phase differences between the push-pull signals of the 1st and 3rd, and 2nd and 4th quadratures.