Optical pickup and optical information recording apparatus using the same
View Patent ↗An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.
1. A beam separation device for an optical pickup configured to separate a laser light beam emitted by a laser light source into at least three light beams comprising:
the beam separation device being divided into first, second and third areas, each of which has a prescribed periodic structure,
the first area is placed between the second and third areas,
the second area has periodic structure that is shifted from that of the first area by approximately 90° in the phase of the periodic structure, and
the third area has periodic structure that is shifted from that of the second area by approximately 180° in the phase of the periodic structure.
2. The beam separation device according to claim 1 , wherein the width of said first area is narrower than the width of said second area and said third area.