Tilt sensor, optical disk, and tilt compensating method for performing a stable tilt compensating control, and apparatus utilizing the same

摘要

According to the present invention, an apparatus for optically performing recording of information and/or reproduction of information for an optical disk having a recording surface is provided. The apparatus includes: an optical pickup for forming a first light spot on the recording surface; a tilt sensor, arranged to be transported with the optical pickup, for detecting a tilt of the optical disk with respect to an optical axis of the optical pickup by forming a second light spot on the recording surface; and a tilt compensating mechanism for angularly adjusting the optical pickup to eliminate the tilt. In this apparatus, the second light spot (20f) is formed at such a position that a line between the first (93) and second light spots is inclined to a direction perpendicular to the radial direction of the optical disk. This prevents the second light spot from entering mirror regions having no pits or no grooves, even when the first light spot is located on the inner circumference of an information recording region having pits or grooves or on the outer circumference of the information recording region. In another embodiment an optical disk comprises a tilt detecting region inside the recording region. In another aspect, the tilt sensor comprises a diaphragm means for limiting the width of the light beam in a predetermined direction. In another aspect the tilt sensor comprises a light source emitting light in a predetermined wavelength range for which there is equal reflectance for crystalline and amorphous portions of a phase-change-type optical disk.