OPTICAL HEAD AND RECORDING/REPRODUCING DEVICE

摘要

An optical head comprising an objective lens having a large numerical aperture of 0.8 or more. The head further comprises a light source and an aberration-correcting lens group. To correct spherical aberration due to the manufacturing errors of an optical recording medium and lenses, to sufficiently correct chromatic aberration due to the use of a short-wavelength semiconductor laser and to correct aberration resulting from the use of the same optical system for light beams of different wavelengths, the objective lens 20 is composed of two more lenses and has a numerical aperture of 0.80 or more and the aberration-correcting lens group 1 is composed of a positive lens group 3 and a negative lens group 2. The space between the positive lens group 3 and negative lens group 2 of the aberration-correcting lens group 1 is changed, thereby to correct spherical aberration occurring at each optical surface of the optical system. <IMAGE>