Optical pick-up utilizing a phase diffraction grating for diffracting reflected light in two directions

摘要

An optical pickup for recording and reproducing information via a magneto-optical disk comprises a phase-diffraction grating which is diffracted in two directions perpendicular to each other on a plane perpendicular to a beam axis. The diffracted light of the phase-diffraction grating has a different phase for each direction, and the phases are varied according to the polarization angle which is rotated by the Kerr effect of the magneto-optical disk. The reproduction signal is detected using the intensity variation of the diffracted light of the two directions due to the phase change. Also, the focus error signal according to the oscillation of the magneto-optical disk is detected by condensing the diffracted light of the phase-diffraction grating by means of the condensing lens and using the amplitude change of the diffracted light. Such an optical pickup is not affected by the variation of the light quantity, thereby contributing to clear reproduction and the enhancement of the signal-to-noise ratio.