OPTICAL RECORDING AND/OR REPRODUCING DEVICE AND OPTICAL RECORDING AND/OR REPRODUCING METHOD

摘要

PROBLEM TO BE SOLVED: To surely perform focus control of a light beam irradiating an optical recording medium of a land groove recording system. SOLUTION: The light beam exited from a light source 13 is branched into a main beam and an auxiliary beam by a diffraction grating 15. The light beam irradiating an optical disk 2 and being reflected from the optical disk 2 is made incident on a photodetector 20 through a cylindrical lens 19. A focus error signal is generated from return light of the main beam and the auxiliary beam which are made incident on the photodetector 20, and an information signal is recorded and/or reproduced while performing focus control of the main beam based on the focus error signal.